1. Field of the Invention
This invention relates to an ink jet recording method, particularly to an ink jet recording method for use with paper generally used in office or home.
2. Related Background Art
Heretofore, various methods have been investigated and proposed for ink jet recording them, so-called the Drop-on-Demand system using paper as the recording medium. Detailed investigations have been made about ink, paper and mechanisms of the printer, etc., since miniaturization of the instrument is possible and the application of the system is extremely broad.
However, the jet printers employing the Drop-on-Demand system of the prior art have several problems, and the greatest problem is that paper generally used in office and home, etc., such as note, report paper, copying paper, letter paper, postcard, etc., cannot be used.
That is, when printing is performed with the various papers mentioned above in a prior art ink jet printer employing the Drop-on-Demand system, printed ink is spread along the fibers of the paper, whereby the shape of the dot becomes indefinite resulting in so-called feathering, therefore, fine rulings, or fine letters for complicated Chinese characters defined by the JIS second standard becomes indistinct and difficult to read in most cases.
Further, the paper mentioned above are frequently treated with sizing in their manufacture so that feathering may be difficult when writing is performed with a writing implement employing an aqueous ink. Similarly when printing is effected with an ink jet printer, penetration of the ink into the paper becomes difficult making the drying characteristics of the ink at the printed portion unsuitable, whereby for example the printed letters maybe contaminated by rubbing with the cover of the printer, and/or that the ink may be attached to hand when the printed matter is touched with hand.
Accordingly, various improvements have been made for the purpose of improving feathering and drying characteristic of the printed letters. For example, in Unexamined Japanese Patent Publication No. 57862/1981, the pH of ink is made strongly alkaline, in Unexamined Japanese Patent Publication No. 29546/1980 a large amount of surfactant is added in the ink, and in Japanese Patent Publication No. 13675/1983 a water-soluble polymer is added in the ink. The method of making the pH of ink strongly alkaline involves the drawbacks such that, for example, it is dangerous when ink is touched with hands, and also both feathering and drying characteristic are not good for papers using a certain kind of sizing agent. In the method in which a large amount of surfactant is added, troubles are seen such that feathering is variable depending on the paper, or the ink may be retracted from the orifice surface depending on the condition of the printer head whereby no ink is ejected, alternatively by wetting of the whole surface of the orifice no ink will be ejected, etc. Further, according to the method in which a water-soluble polymer is added to ink, although feathering and drying characteristics of printed letters are improved in some extent, problems remain such as the ink tends to be dried at the orifice tip of the printer head, and also that normal ejecting is effected when the printer is left to stand in the room for several minutes in a nonprinting state.
Other ink jet recording methods have been proposed to overcome feathering and improve drying characteristics of printed documents. However, these methods have also been unsuccessful in overcoming the drawbacks associated with conventional recording. For instance, U.S. Pat. No. 4,243,994, relating to a liquid ejection printer, taught that it was desirable to utilize ink droplets having a preferred thermal expansion coefficient of between 0.5 and 1.5, a viscosity of between 0.3 and 3.0 centipoise at 20.degree. C., a preferred thermal conductivity of between 1 and 10 (.times.10.sup.3 W.cm.deg), a preferred surface tension of between 10 and 60 (dyne/cm) and a preferred pH of between 8 and 11. U.S. Pat. No. 4,345,262, relating to a thermal ink jet printer, taught that droplet adhesion on recording paper was improved when recording was effected by keeping the recording paper away from the position of the discharge orifice by 1.5 mm to 3.0 mm with the "flying speed" of the liquid droplet being approximately 5 m/sec and the moving speed of the recording paper being 0.1 m/sec. U.S. Pat. No. 4,642,654, relating to ink jet printing on coated paper, taught that the diameter of liquid ink droplets of is usually 20-1000 .mu.m and results are good when the particle size d of the filter and the diameter of the liquid droplet D satisfies the relation that d/D is between 0.03 and 0.3. When d/B is less than 0.03, the amount of the binder for the filler must be significantly decreased so as to obtain a necessary ink absorbing capacity. When the amount of the binder is so decreased, the receiving layer may exfoliate and the receiving member is not practically usable. On the other hand, when d/D exceeds 0.3, the circulatory of the printed dot is lower and poor images result. Accordingly, each of the patents discussed above have independently taught several different approaches to improve recording. However, none of the art discussed above has solved the problems associated with drop-on-demand ink jet recording on a recording medium which has been subjected to sizing, having fibers exposed on its surface, as done in the present invention.
Accordingly, various methods have been attempted for improvement of the mechanisms of printers other than the improvement of ink as mentioned above, but no ink jet recording methods have solved all of the problems such as feathering, drying characteristics of printed letters, drying prevention of ink at the printer head, etc.